linux - TTY keeps pressing enter

I can't login to my ttys. The following happens:

1. I open any tty using Ctrl+Alt+Number


2. I enter my username


3. I press "enter"


4. The password is skipped due to another "enter"


5. After a few seconds the login name prompt and is getting skipped as well as the password prompt again.


6. Step 5 repeats infinitely.

=> So an "enter" is occurring again and again.

This effect appears to be only on ttys. On any other console/terminal/program whatever this does not occur at all.

Where could this problem even arise from?

EDIT: This problem appears on my PC (external keyboard) as well as on my laptop.